A risk control device and method for volatile organic pollution sites

Abstract

The present invention belongs to the technical field of risk control of contaminated sites, and discloses a risk control device and method for volatile organic contaminated sites, which can realize the continuous removal of VOCs. The device includes a first online monitoring unit, a system control unit, a VOCs pollution reduction unit and a groundwater monitoring well; the VOCs pollution reduction unit includes a first groundwater extraction well body, a second groundwater extraction well body, a first microorganism culture tank, a second microorganism culture tank, a first reagent tank, a second reagent tank, a water level monitor, and an injection pipe assembly, and the injection pipe assembly includes a first injection pipe and a second injection pipe. The system control unit is used to send a monitoring instruction to the first online monitoring unit, and adjust the operation of the water pump to control the bacterial liquid culture volume and output volume of the first microorganism culture tank and the second microorganism culture tank respectively.

Description

Technical Field

[0001] The present invention relates to risk control of contaminated sites, and in particular to a risk control device and method for volatile organic contaminated sites. Background Art

[0002] Compared with heavy metal and semi-volatile organic compound contaminated sites, volatile organic compounds (VOCs) represented by benzene and chlorinated hydrocarbons have higher volatility and mobility, more hidden and diverse exposure pathways, and are more difficult to investigate, evaluate, remediate and manage, with greater potential harm to human health. The environmental management of VOCs contaminated sites is the focus and difficulty of environmental protection work.

[0003] At present, vertical barrier and horizontal barrier technologies are mostly used to control site pollution risks. The control method is single and does not take into account the continuous removal of pollutants. Not only is the investment cost high, but it also does not meet the current green and low-carbon development requirements. Vertical barrier technology is to set up a vertical barrier layer around the risk control area of ​​the polluted site to block the spread of pollutants, including soil-bentonite isolation wall, high-pressure jet grouting wall, mixing pile wall and other technologies. Horizontal barrier technology is to set up a horizontal barrier layer on the surface or bottom of the risk control area of ​​the polluted site to block the spread of pollutants and direct contact with the protected population, including concrete horizontal barrier, clay horizontal barrier, flexible horizontal barrier and other technologies.

[0004] In addition, the traditional risk control method of isolation lacks real-time warning and control effect evaluation functions, and cannot adjust control measures in time according to actual conditions. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a risk control device and method for volatile organic polluted sites, which can achieve continuous removal of VOCs.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a risk control device for a volatile organic polluted site, wherein the polluted site includes a risk control area, and the device includes a first online monitoring unit, a system control unit, a VOCs pollution reduction unit and a groundwater monitoring well; wherein the VOCs pollution reduction unit includes a first groundwater extraction well body, a second groundwater extraction well body, a first microorganism culture tank, a second microorganism culture tank, a first reagent tank, a second reagent tank, a water level monitor, and an injection pipe assembly, wherein the injection pipe assembly includes a first injection pipe and a second injection pipe; the first groundwater extraction well body, the second groundwater extraction well body, the first injection pipe and the second injection pipe are all located in the risk control area, the lower part of the first injection pipe is located in the upper soil layer of the soil surface, and the lower part of the second injection pipe is located in the lower soil layer of the soil surface; the outlet of the first reagent tank is connected to the inlet of the first microorganism culture tank, the outlet of the first microorganism culture tank is connected to the first injection pipe through a first pipeline, and the first groundwater extraction well body is connected to the inlet of the first microorganism culture tank through a water pump ; The outlet of the second reagent tank is connected to the inlet of the second microorganism culture tank, the outlet of the second microorganism culture tank is connected through the second pipeline and the second injection pipe, and the second groundwater extraction well is connected to the inlet of the second microorganism culture tank through a water pump; the water level monitor is located in the first groundwater extraction well or the second groundwater extraction well, and the groundwater monitoring well, for monitoring the groundwater level of the contaminated site, and transmitting the water level information to the system control unit; the groundwater monitoring well is located in the contaminated site and outside the risk control area, and the groundwater monitoring well is used to monitor the groundwater level and the groundwater VOCs content; the first online monitoring unit is located in the risk control area, for collecting and storing surface VOCs content and soil moisture data, and uploading them to the system control unit; the system control unit is used to receive the information transmitted by the first online monitoring unit and the information transmitted by the water level monitor, and is also used to issue monitoring instructions to the first online monitoring unit, and adjust the water pump to control the bacterial liquid culture volume and output volume of the first microorganism culture tank and the second microorganism culture tank respectively.

[0008] As a preferred example, the first online monitoring unit includes a hollow shell with an opening, a VOCs detection module, and a soil moisture detection module including a soil moisture sensor; the opening of the hollow shell is in contact with the soil to form a closed space; the soil moisture sensor is located in the hollow shell and in the soil; the hollow shell is connected to the VOCs detection module through a gas pipeline; the VOCs detection module and the soil moisture detection module are respectively connected to the system control unit.

[0009] As a preferred example, the device also includes an ecological restoration unit, which covers the risk control area and includes a clean soil layer or a planting soil layer, and plants planted on the clean soil layer or the planting soil layer.

[0010] As a preferred example, the ecological regreening unit further includes a slurry layer, and the slurry layer is located below the clean soil layer or the planting soil layer.

[0011] As a preferred example, the first microorganism culture tank is used for enrichment culture of aerobic bacteria, and the second microorganism culture tank is used for enrichment culture of facultative bacteria to anaerobic bacteria.

[0012] As a preferred example, the first injection pipe is buried in the soil at a depth ranging from 10 to 40 cm, and the portion of the first injection pipe 5 to 40 cm below the ground is a sieve tube; the second injection pipe is buried in the soil at a depth ranging from 40 to 100 cm, and the portion of the second injection pipe 30 to 100 cm below the ground is a sieve tube.

[0013] As a preferred example, the device also includes a second online monitoring unit, which is located in the contaminated site and outside the risk control area; the second online monitoring unit is close to the risk control area; the second online monitoring unit is used to monitor the surface VOCs content outside the risk control area.

[0014] As a preferred example, the injection pipe assemblies are at least six groups and are evenly distributed in the risk control area; there are four groundwater monitoring wells and four second online monitoring units, which are distributed outside the risk control area.

[0015] In a second aspect, the present invention further provides a method for risk management of contaminated sites, comprising:

[0016] Step 10: Obtain the type and content of VOCs in the risk control area of ​​the contaminated site, and set the thickness of the clean soil layer or the planting soil layer, or the thickness of the clean soil layer or the planting soil layer and the thickness of the slurry layer, so that the content of VOCs volatilized from the clean soil layer or the planting soil layer in the risk control area is lower than the detection limit;

[0017] Step 20, compacting the soil in the risk control area, and then covering the risk control area with a clean soil layer or a planting soil layer according to the thickness obtained in step 10, or setting a slurry layer, a clean soil layer or a planting soil layer from bottom to top above the risk control area; and planting vegetation on the clean soil layer or the planting soil layer;

[0018] Step 30: Collect surface VOCs content and soil moisture data in the risk control area through the VOCs detection module and the soil moisture detection module, and collect water level data in the first groundwater extraction well or the second groundwater extraction well, and the groundwater monitoring well through the water level monitor;

[0019] Step 40: Control the operation of the VOCs pollution reduction unit according to the surface VOCs content and soil moisture data, as well as the water level data in the risk control area.

[0020] As a preferred example, the step 40 specifically includes:

[0021] Start the first groundwater extraction well and the second groundwater extraction well to extract groundwater, and control the groundwater extraction flow rate at 10-5000mL / min; start the first microbial culture tank and the second microbial culture tank to inject bacterial solution into the surface soil; when the water level elevation of the first groundwater extraction well or the second groundwater extraction well is lower than the water level elevation of the groundwater monitoring well, and the water level difference is greater than the preset water level difference value, stop extracting groundwater from the first groundwater extraction well and the second groundwater extraction well; when the total amount of VOCs detected on the surface of the risk control area increases for three consecutive times or is greater than the preset value of the total amount of VOCs, stop injecting bacterial solution into the surface soil from the first microbial culture tank and the second microbial culture tank, and stop extracting groundwater from the first groundwater extraction well and the second groundwater extraction well; when the soil moisture is greater than the preset moisture value, stop injecting bacterial solution into the surface soil from the first microbial culture tank and the second microbial culture tank, and stop extracting groundwater from the first groundwater extraction well and the second groundwater extraction well; the preset moisture value is not greater than where ρ s is the soil particle density, unit: kg·dm -3 ρ b is the soil bulk density, unit: kg·dm -3 ρ w is the groundwater density, unit: kg·dm -3 .

[0022] Compared with the prior art, the risk control device and method for volatile organic pollution sites of the embodiments of the present invention can achieve continuous removal of VOCs. The risk control device of the present invention includes a first online monitoring unit, a system control unit, a VOCs pollution reduction unit and a groundwater monitoring well. The system control unit controls the operation of the VOCs pollution reduction unit according to the monitoring data of the online monitoring unit, and the groundwater extraction technology is coupled with the enrichment and cultivation of pollutant-degrading bacteria in the soil at different depths to achieve the blocking of VOCs diffusion and health risks in the risk control area, and the green and sustainable removal of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the device structure of an embodiment of the present invention; the arrows in the figure indicate the flow direction of the bacterial liquid or well water;

[0024] Figure 2 This is a top view of the device according to an embodiment of the present invention in a contaminated site, in which arrows indicate the direction of groundwater flow.

[0025] In the figure, there are: a first groundwater extraction well 1, a second groundwater extraction well 2, a first microorganism culture tank 3, a second microorganism culture tank 4, a first medicine tank 5, a second medicine tank 6, a first injection pipe 7, a second injection pipe 8, a water level monitor 9, a hollow shell 10, a VOCs detection module 11, a soil moisture sensor 12, a soil moisture detection module 13, a groundwater monitoring well 14, a second online monitoring unit 15, a contaminated site 16, and a risk control area 17. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0027] Sites where soil pollutant content exceeds relevant standards are called contaminated sites. Risk control areas refer to the spatial distribution of soil and groundwater pollution within contaminated sites determined based on technical specification surveys and assessments, and the risk control scope further determined in combination with risk control objectives.

[0028] The risk control device for volatile organic polluted sites of the embodiment of the present invention can block the spread of VOCs and the risk to human health, achieve continuous removal of pollutants, and adjust the control method according to actual conditions. Figure 1 and Figure 2As shown, the risk control device includes a first online monitoring unit, a system control unit, a VOCs pollution reduction unit and a groundwater monitoring well 14. The VOCs pollution reduction unit includes a first groundwater extraction well body 1, a second groundwater extraction well body 2, a first microorganism culture tank 3, a second microorganism culture tank 4, a first reagent tank 5, a second reagent tank 6, a water level monitor 9, and an injection pipe assembly, wherein the injection pipe assembly includes a first injection pipe 7 and a second injection pipe 8. The first groundwater extraction well body 1, the second groundwater extraction well body 2, the first injection pipe 7 and the second injection pipe 8 are all located in the risk control area 17, the lower part of the first injection pipe 7 is located in the upper soil layer of the soil surface, and the lower part of the second injection pipe 8 is located in the lower soil layer of the soil surface. The outlet of the first reagent tank 5 is connected to the inlet of the first microorganism culture tank 3, the outlet of the first microorganism culture tank 3 is connected to the first injection pipe 7 through the first pipeline, and the first groundwater extraction well body 1 is connected to the inlet of the first microorganism culture tank 3 through a water pump; the outlet of the second reagent tank 6 is connected to the inlet of the second microorganism culture tank 4, the outlet of the second microorganism culture tank 4 is connected through the second pipeline and the second injection pipe 8, and the second groundwater extraction well body 2 is connected to the inlet of the second microorganism culture tank 4 through a water pump. The water level monitor 9 is located in the first groundwater extraction well body 1 or the second groundwater extraction well body 2, and the groundwater monitoring well 14, and is used to monitor the groundwater level of the contaminated site 16 and transmit the water level information to the system control unit. The groundwater monitoring well 14 is located in the contaminated site 16 and outside the risk control area 17. The groundwater monitoring well 14 is used to monitor the groundwater level and the groundwater VOCs content. The first online monitoring unit is located in the risk control area 17, and is used to collect and store surface VOCs content and soil moisture data, and upload them to the system control unit. The system control unit is used to receive information transmitted by the first online monitoring unit and the information transmitted by the water level monitor 9, and is also used to issue monitoring instructions to the first online monitoring unit and adjust the operation of the water pump to control the culture volume and output volume of the bacterial liquid in the first microbial culture tank 3 and the second microbial culture tank 4 respectively.

[0029] In the above embodiment, the system control unit controls the VOCs pollution reduction unit to work according to the monitoring data of the online monitoring unit, blocks the diffusion of VOCs in the risk control area 17, and realizes the continuous removal of pollutants. The system control unit can adjust the VOCs content, soil moisture, and groundwater level detection frequency, and adjust the water pump, the first microbial culture tank 3, and the second microbial culture tank 4. The bacterial liquid culture and injection. When the water level elevation of the first groundwater extraction well 1 or the second groundwater extraction well 2 is not less than the water level elevation of the groundwater monitoring well 14, the first groundwater extraction well 1 and the second groundwater extraction well 2 are started to extract groundwater. The first reagent tank 5 adds an oxidant or microbial nutrient (one or more of calcium peroxide, hydrogen peroxide, ferrate, yeast extract, molasses, phosphate, urea, nitrate, and magnesium sulfate), and the second reagent tank 6 adds an oxidant or microbial nutrient (one or more of calcium peroxide, hydrogen peroxide, ferrate, lactic acid, yeast extract, methanol, sodium acetate, phosphate, urea, ferrous sulfate, nitrate, and magnesium sulfate). The reagent in the first reagent tank 5 flows into the first microorganism culture tank 3 for enrichment culture of aerobic bacteria. The reagent in the second reagent tank 6 flows into the second microorganism culture tank 4 for enrichment culture of facultative bacteria to anaerobic bacteria. After enrichment culture, the aerobic bacterial liquid in the first microorganism culture tank 3 flows into the first injection pipe 7 through the first pipeline, and then flows into the surrounding soil through the first injection pipe 7.

[0030] Since the lower part of the first injection pipe 7 is located in the upper layer of soil on the surface of the soil, the injected microorganisms can promote the growth of the plants, build a biological reaction barrier, and effectively block the spread of VOCs and human health risks: plant root secretions enhance microbial activity and improve the microbial removal efficiency of benzene, low-chlorinated hydrocarbons and other secondary pollutants in the soil; vegetation covers the surface of the soil, effectively reducing the entry of VOCs and soil particles into the ambient air.

[0031] The first microorganism culture tank 3 is provided with an exhaust gas treatment device connected thereto to prevent the direct discharge of volatile pollutants. The exhaust gas treatment device may be an activated carbon adsorption device.

[0032] After enrichment and cultivation, the facultative bacteria liquid and anaerobic bacteria liquid in the second microorganism culture tank 4 flow into the second injection pipe 8 through the second pipeline, and then flow into the surrounding soil through the second injection pipe 8. Since the lower part of the second injection pipe 8 is located in the lower soil layer of the soil surface, the target pollutant degradation bacteria are enriched, the biological dechlorination efficiency of high-chlorine-substituted hydrocarbon pollutants in this layer in anaerobic and anoxic environments and the degradation of pollutants such as benzene series are enhanced, and the generated volatile products such as low-chlorine-substituted hydrocarbons and unreacted VOCs are gradually degraded by the enhanced aerobic microorganisms in the upper soil layer of the soil surface during the process of continuing to migrate upward.

[0033] In the first groundwater extraction well 1, the groundwater is pumped into the first microbial culture tank 3 by a water pump to enrich and culture pollutant-degrading bacteria. The groundwater contains indigenous microorganisms of the plot, which have more VOCs-specific microbial degradation bacteria under long-term environmental acclimation conditions. The groundwater is extracted into the first microbial culture tank 3, and targeted agents are added to stimulate the growth of VOCs-specific microbial degradation bacteria, thereby simultaneously removing VOCs from the groundwater.

[0034] Similarly, in the second groundwater extraction well 2, the groundwater is pumped into the second microbial culture tank 4 by a water pump to enrich and culture pollutant-degrading bacteria. The groundwater contains indigenous microorganisms of the plot, and the indigenous microorganisms of the plot have more VOCs-specific microbial degradation bacteria under long-term environmental acclimation conditions. The groundwater is extracted into the second microbial culture tank 4, and the growth of VOCs-specific microbial degradation bacteria is stimulated by adding targeted agents, and VOCs in the groundwater are removed simultaneously.

[0035] The bacterial liquid enters the soil layers at different depths through the first injection pipe 7 and the second injection pipe 8. Extracting groundwater can form a hydraulic control effect, the groundwater level is lowered, and the surrounding water and pollutants will converge to the pumping point, slowing down the migration of pollutants to the outside of the risk control area 17, thereby achieving the purpose of preventing and controlling the risk of diffusion. When the water level elevation of the first groundwater extraction well 1 or the second groundwater extraction well 2 is not less than the groundwater monitoring well 14, the first groundwater extraction well 1 and the second groundwater extraction well 2 are started to extract groundwater.

[0036] The reagents stored in the first reagent tank 5 and the second reagent tank 6 are one or more of calcium peroxide, hydrogen peroxide, ferrate, lactic acid, yeast extract, methanol, sodium acetate, molasses, phosphate, urea, nitrate, and magnesium sulfate. The reagents actually used in the first reagent tank 5 and the second reagent tank 6 are determined according to the working conditions or the type and degree of pollution of VOCs.

[0037] The well water extracted from the first groundwater extraction well 1 and the second groundwater extraction well 2 contains some pollutants, which can inhibit the growth of non-specific degradation bacteria and promote the growth and enrichment of target microorganisms. In order to prevent pollutants from re-entering the soil and groundwater, it is necessary to ensure sufficient culture time in the first microbial culture tank 3 and the second microbial culture tank 4. For example, the continuous culture time for easily degradable benzene series is more than 2 days, and the continuous culture time for chlorinated hydrocarbons is more than 7 days. The culture time is related to the concentration of pollutants, culture temperature, nutrient levels, etc. By arranging VOCs detection devices at the top of the first microbial culture tank 3 and the second microbial culture tank 4, respectively, when the VOCs concentration detected by the VOCs detection device is lower than 5ppm (the preset value can be determined according to the type of target pollutant), the culture solution can be discharged.

[0038] In the above embodiment, the bacterial liquid flowing out through the second injection pipe 8 reduces VOCs in the lower layer of the soil surface, and the bacterial liquid flowing out through the first injection pipe 7 reduces VOCs in the upper layer of the soil surface, as well as VOCs flowing from the lower layer to the upper layer.

[0039] As a preferred example, the first online monitoring unit includes a hollow shell 10 having an opening, a VOCs detection module 11, and a soil moisture detection module 13 including a soil moisture sensor 12. The opening of the hollow shell 10 is in contact with the soil to form a closed space. The soil moisture sensor 12 is located in the hollow shell 10 and in the soil. The hollow shell 10 is connected to the VOCs detection module 11 through a gas pipeline. The VOCs detection module 11 and the soil moisture detection module 13 are respectively connected to the system control unit. The first online monitoring unit is located in the risk control area 17. The VOCs volatilized from the soil in the hollow shell 10 are enclosed in the hollow shell 10. The VOCs detection module 11 can be used to detect the VOCs content in the hollow shell 10. The soil moisture sensor 12 can be used to detect the soil moisture content.

[0040] As a preferred example, the device also includes an ecological regreening unit, which covers the risk control area 17, and includes a clean soil layer or a planting soil layer, and plants planted on the clean soil layer or the planting soil layer. Covering the risk control area 17 with an ecological regreening unit can achieve physical isolation of VOCs, making it difficult for VOCs in the soil to flow out. After the surface soil is compacted, it is covered with a 5 to 20 cm thick clean soil layer or a planting soil layer. The sown plants are one or more of ryegrass, alfalfa, dog grass, cattail, schisandra, sedge and ramie.

[0041] As a preferred example, the ecological restoration unit also includes a slurry layer, and the slurry layer is located below the clean soil layer or the planting soil layer. For the risk control area 17 with a lot of mixed construction waste or mainly coarse sand soil, after the surface layer is compacted, a 1-5 cm thick slurry layer of bentonite or other clay or mixture is sprayed, and then covered with a clean soil layer or a planting soil layer. Generally, the surface soil of the site is miscellaneous fill soil with large pores and good air permeability, which is conducive to the volatilization of VOCs and needs to be compacted. On the one hand, fine-grained bentonite and clay fill part of the pores, and on the other hand, the slurry layer formed has poor air permeability.

[0042] Plants are planted in the clean soil layer or the planting soil layer, and the root system may pass through the slurry layer and the compaction layer. The second injection pipe 8 passes through the slurry layer, the clean soil layer or the planting soil layer, and the compaction layer. The first injection pipe 7 does not necessarily pass through the compaction layer.

[0043] As a preferred example, the first injection pipe 7 is buried in the soil at a depth of 10 to 40 cm, and the portion of the first injection pipe 7 5 to 40 cm below the ground is a sieve pipe; the second injection pipe 8 is buried in the soil at a depth of 40 to 100 cm, and the portion of the second injection pipe 8 30 to 100 cm below the ground is a sieve pipe. The sieve pipe is filled with filter material around it, allowing the bacterial solution to diffuse into the surrounding soil after entering the first injection pipe 7 or the second injection pipe 8.

[0044] As a preferred example, the device further includes a second online monitoring unit 15. The second online monitoring unit 15 is located in the contaminated site 16 and outside the risk control area 17; the second online monitoring unit 15 is close to the risk control area 17; the second online monitoring unit 15 is used to monitor the surface VOCs content outside the risk control area 17.

[0045] If the water level detected by the groundwater monitoring well 14 is lower than the water level of the extraction well in the risk control area, it means that the groundwater is flowing out of the risk control area. In this case, the first groundwater extraction well 1 and the second groundwater extraction well 2 need to be started.

[0046] If the second online monitoring unit 15 detects that the surface VOCs content outside the risk control area 17 is greater than the preset value, it means that the pollution may spread, and it is necessary to evaluate whether the existing risk control measures are ineffective, and take other control or repair measures if necessary.

[0047] If the VOCs content in the groundwater monitored by groundwater monitoring well 14 continues to increase, it means that the pollution may spread and the existing risk control measures are ineffective. It is necessary to evaluate whether the existing risk control measures are ineffective and take other control or remediation measures if necessary.

[0048] In order to improve the efficiency of VOCs reduction, the injection pipe assembly is at least six groups, and is evenly distributed in the risk control area 17; there are four groundwater monitoring wells 14 and four second online monitoring units 15, which are distributed outside the risk control area 17. Multiple groups of injection pipe assemblies are set in the risk control area 17, which can work simultaneously to evenly inject the bacterial liquid into the risk control area 17. Groundwater monitoring wells 14 and second online monitoring units 15 are set around the outside of the risk control area 17, respectively, to achieve multi-directional monitoring, and improve the accuracy, timeliness and effectiveness of risk control measures.

[0049] The method for performing risk control of a contaminated site using the risk control device of the above embodiment comprises the following steps:

[0050] Step 10: Obtain the type and content of VOCs in the risk control area 17 of the contaminated site, and set the thickness of the clean soil layer or the planting soil layer, or the thickness of the clean soil layer or the planting soil layer and the thickness of the slurry layer, so that the content of VOCs volatilized from the clean soil layer or the planting soil layer in the risk control area 17 is lower than the detection limit. The content of VOCs volatilized from the clean soil layer or the planting soil layer is lower than the detection limit, which means that the diffusion of VOCs is effectively blocked.

[0051] Step 20, compact the soil in the risk control area 17, and then cover the risk control area 17 with a clean soil layer or a planting soil layer according to the thickness obtained in step 10, or set a slurry layer, a clean soil layer or a planting soil layer from bottom to top above the risk control area 17; plant vegetation on the clean soil layer or the planting soil layer.

[0052] A clean soil layer or a planting soil layer with a certain thickness and a slurry layer with a certain thickness are set up, so that less VOCs flow out of the soil in the risk control area 17. The clean soil layer or the planting soil layer and the slurry layer are set up to achieve physical isolation of VOCs.

[0053] Step 30: collect the surface VOCs content and soil moisture data of the risk control area 17 through the VOCs detection module 11 and the soil moisture detection module 13, and collect the water level data in the first groundwater extraction well 1 or the second groundwater extraction well 2, and the water level data in the groundwater monitoring well 14 through the water level monitor 9;

[0054] Step 40: Control the operation of the VOCs pollution reduction unit according to the surface VOCs content and soil moisture data, as well as the water level data of the risk control area 17.

[0055] The step 40 specifically includes:

[0056] Step 401 starts the first groundwater extraction well 1 and the second groundwater extraction well 2 to extract groundwater, and the extraction groundwater flow rate is controlled at 10-5000 mL / min; starts the first microorganism culture tank 3 and the second microorganism culture tank 4 to inject bacterial solution into the surface soil.

[0057] Step 402: When the water level elevation of the first groundwater extraction well 1 or the second groundwater extraction well 2 is lower than the water level elevation of the groundwater monitoring well 14, and the water level difference is greater than the preset water level difference value, the first groundwater extraction well 1 and the second groundwater extraction well 2 are stopped from extracting groundwater;

[0058] When the total amount of VOCs detected on the surface of the risk control area 17 increases three times in a row or is greater than the preset value of the total amount of VOCs, the first microbial culture tank 3 and the second microbial culture tank 4 are stopped from injecting bacterial solution into the surface soil, and the first groundwater extraction well 1 and the second groundwater extraction well 2 are stopped from extracting groundwater. When the total amount of VOCs detected on the surface of the risk control area 17 increases continuously or is greater than the preset value of the total amount of VOCs, it is usually due to the accumulation of residual VOCs in the injected bacterial solution. The measure to be taken is to shut down the injection of bacterial solution and further extend the culture time, so the injection of the first injection pipe 7 and the second injection pipe 8 is stopped, and the first groundwater extraction well 1 and the second groundwater extraction well 2 are stopped from extracting groundwater;

[0059] When the soil moisture is greater than the preset moisture value, the first microorganism culture tank 3 and the second microorganism culture tank 4 are stopped from injecting bacterial solution into the surface soil, and the first groundwater extraction well 1 and the second groundwater extraction well 2 are stopped from extracting groundwater; the preset moisture value is not greater than where ρ s is the soil particle density, unit: kg·dm -3 ρ b is the soil bulk density, unit: kg·dm -3 ρ w is the groundwater density, unit: kg·dm -3 . Excessive soil moisture is not conducive to plant growth.

[0060] In step 30 and step 40, bacterial liquid is added to the soil, and the bacterial liquid reacts with VOCs to reduce VOCs in the soil, thereby further reducing the volatilization of VOCs from the ecological restoration unit.

[0061] When the total surface VOCs detection value of the risk control area 17 continues to decrease (for example, the total surface VOCs detection value decreases for three consecutive times) and is lower than the VOCs preset value, and the soil moisture is lower than the moisture preset value, restart the first microbial culture tank 3 and the second microbial culture tank 4 to inject bacterial solution into the surface soil, and start the first groundwater extraction well 1 and the second groundwater extraction well 2 to extract groundwater.

[0062] When the VOCs content detected in real time by the second online monitoring unit 15 and the groundwater VOCs content detected by the groundwater monitoring well 14 continue to increase (for example, the groundwater VOCs content monitoring increases for three consecutive times), it means that the pollution may spread, and it is necessary to evaluate whether the existing risk control measures are ineffective, and take other control or remediation measures if necessary.

[0063] The embodiments of the present invention continuously reduce the upward migration of volatile organic pollutants by compacting the soil, spraying bentonite or clay slurry, covering with clean soil, and restoring vegetation. According to the pollution characteristics, the indigenous microorganisms of the plot are propagated in situ in a targeted manner, and injected into the surface soil (0-1m) in layers to achieve the enrichment of volatile organic pollutant-degrading bacteria in the surface soil layer, enhance the efficiency of microorganisms in removing pollutants, and further reduce the upward migration of volatile organic pollutants. The method of the present application requires little investment and is long-lasting. It can be operated for a long time at low cost, and can block the migration and diffusion of volatile organic pollutants and health risks, and continuously remove organic pollutants.

[0064] The embodiment of the present invention realizes the in-situ ex situ enrichment and layered injection of volatile organic pollutant degradation bacteria. Specifically, the first microbial culture tank 3 can be used for enrichment culture of aerobic bacteria, and the second microbial culture tank 4 can be used for enrichment culture of facultative bacteria to anaerobic bacteria, and are respectively connected to the first injection pipe 7 and the second injection pipe 8. The first injection pipe 7 and the second injection pipe 8 are respectively located in the upper soil and the lower soil of the surface layer. The dominant microorganisms in the upper soil are aerobic bacteria. The dominant microorganisms in the lower soil are facultative bacteria to anaerobic bacteria. The soil layer affected by the first injection pipe 7 just promotes the greening plants. Microorganisms can promote plant growth, and the root secretions produced by plants can promote the growth of microorganisms and better volatilize in their respective systems. The degradation of VOCs by microorganisms in the lower soil is enhanced by the second injection pipe 8. VOCs and secondary pollutants that are not completely degraded migrate upward, and when they pass through the influence range of the first injection pipe 7, they are further biodegraded by the microorganisms enhanced in this area. This achieves the reduction of VOCs layer by layer.

[0065] The types of VOCs in contaminated sites are generally mainly benzene series and chlorinated hydrocarbons, among which benzene series pollutants are mainly degraded by aerobic microorganisms; high-chlorine-substituted hydrocarbon pollutants such as trichloroethylene are first dechlorinated in anaerobic and anoxic environments to produce low-chlorine-substituted hydrocarbons, and the volatile products continue to migrate upward and gradually undergo aerobic biodegradation.

[0066] The embodiment of the present invention integrates physical barriers and pollution biodegradation to achieve green and low-carbon risk management methods. Specifically, in this embodiment, the surface soil layer of the risk control area 17 is compacted; the slurry layer is sprayed; the clean soil layer or planting soil layer is covered; and the moisture content of the soil is regulated. This is a physical barrier to VOCs in the soil. The enhanced microorganisms injected into the soil and the plants for ecological restoration of the surface soil are injected through the first injection pipe 7 and the second injection pipe 8. This is an enhanced biological barrier.

[0067] Compacting the topsoil can reduce the pores in the soil layer and reduce the diffusion of volatile gases into the outside air through the pores. Properly increasing the moisture content of the upper surface soil can not only promote plant growth, but also reduce the volume ratio of air in the soil pores and reduce the upward diffusion rate of volatile pollutants.

[0068] The two barriers work together to prevent and control the risk of VOCs volatilization.

[0069] In the physical barrier, the soil moisture content is regulated by adjusting the amount of bacterial solution output from the first microbial culture tank 3 and the second microbial culture tank 4 and extracting groundwater from the extraction well. After the bacterial solution enters the soil surface, the soil moisture will gradually increase. In order to avoid excessive moisture affecting crop growth, a soil moisture sensor 12 is set to monitor the moisture of the surface soil (such as 0-20cm). When the moisture is too high, for example, the soil moisture reaches a preset value (not more than ), the system control unit is used to feedback and adjust the injection amount of the bacterial solution and the amount of groundwater extracted by the first groundwater extraction well 1 and the second groundwater extraction well 2. In addition, when the VOCs value monitored by the first online monitoring unit continues to increase, the injection amount of the bacterial solution and the amount of groundwater extracted by the extraction well can also be regulated by the system control unit.

[0070] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above specific embodiments, and the descriptions in the above specific embodiments and the specification are only for further illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed for protection.

Claims

1. A risk control device for volatile organic pollution sites, characterized in that: The contaminated site (16) includes a risk control area (17), and the device includes a first online monitoring unit, a system control unit, a VOCs pollution reduction unit and a groundwater monitoring well (14); wherein: The VOCs pollution reduction unit comprises a first groundwater extraction well (1), a second groundwater extraction well (2), a first microorganism culture tank (3), a second microorganism culture tank (4), a first reagent tank (5), a second reagent tank (6), a water level monitor (9), and an injection pipe assembly, wherein the injection pipe assembly comprises a first injection pipe (7) and a second injection pipe (8); The first groundwater extraction well body (1), the second groundwater extraction well body (2), the first injection pipe (7) and the second injection pipe (8) are all located in the risk control area (17), the lower part of the first injection pipe (7) is located in the upper soil layer of the soil surface, and the lower part of the second injection pipe (8) is located in the lower soil layer of the soil surface; The outlet of the first reagent tank (5) is connected to the inlet of the first microorganism culture tank (3), the outlet of the first microorganism culture tank (3) is connected to the first injection pipe (7) via a first pipeline, and the first groundwater extraction well body (1) is connected to the inlet of the first microorganism culture tank (3) via a water pump; the outlet of the second reagent tank (6) is connected to the inlet of the second microorganism culture tank (4), the outlet of the second microorganism culture tank (4) is connected to the second pipeline and the second injection pipe (8), and the second groundwater extraction well body (2) is connected to the inlet of the second microorganism culture tank (4) via a water pump; The water level monitor (9) is located in the first groundwater extraction well (1) or the second groundwater extraction well (2), and the groundwater monitoring well (14), and is used to monitor the groundwater level of the contaminated site (16) and transmit the water level information to the system control unit; The groundwater monitoring well (14) is located in the contaminated site (16) and outside the risk control area (17). The groundwater monitoring well (14) is used to monitor the groundwater level and the VOCs content in the groundwater; The first online monitoring unit is located in the risk control area (17) and is used to collect and store surface VOCs content and soil moisture data and upload them to the system control unit; The system control unit is used to receive information transmitted by the first online monitoring unit and information transmitted by the water level monitor (9), and is also used to issue monitoring instructions to the first online monitoring unit and adjust the operation of the water pump to control the bacterial liquid culture volume and output volume of the first microorganism culture tank (3) and the second microorganism culture tank (4) respectively; It also includes an ecological restoration unit, which covers the risk control area (17), and includes a clean soil layer or a planting soil layer, and plants planted on the clean soil layer or the planting soil layer; The ecological restoration unit further comprises a slurry layer, which is located below the clean soil layer or the planting soil layer; The first microorganism culture tank (3) is used for enrichment culture of aerobic bacteria, and the second microorganism culture tank (4) is used for enrichment culture of facultative anaerobic bacteria.

2. The device according to claim 1, characterized in that The first online monitoring unit comprises a hollow housing (10) having an opening, a VOCs detection module (11), and a soil moisture detection module (13) comprising a soil moisture sensor (12); The opening of the hollow shell (10) is in contact with the soil to form a closed space; the soil moisture sensor (12) is located in the hollow shell (10) and in the soil; the hollow shell (10) is connected to the VOCs detection module (11) via a gas pipeline; and the VOCs detection module (11) and the soil moisture detection module (13) are respectively connected to a system control unit.

3. The device according to claim 1, characterized in that The first injection pipe (7) is buried in the soil to a depth ranging from 10 to 40 cm, and the portion of the first injection pipe (7) 5 to 40 cm below the ground is a screen pipe; The second injection pipe (8) is buried in the soil to a depth ranging from 40 to 100 cm, and the portion of the second injection pipe (8) 30 to 100 cm below the ground is a screen pipe.

4. The device according to claim 1, characterized in that The system further comprises a second online monitoring unit (15), wherein the second online monitoring unit (15) is located in the contaminated site (16) and outside the risk control area (17); the second online monitoring unit (15) is close to the risk control area (17); and the second online monitoring unit (15) is used to monitor the surface VOCs content outside the risk control area (17).

5. The device according to claim 4, characterized in that The injection pipe assemblies are at least six groups and are evenly distributed in the risk control area (17); the groundwater monitoring wells (14) and the second online monitoring units (15) are four each and are distributed outside the risk control area (17).

6. A method for risk control of contaminated sites using the risk control device according to claim 1, characterized in that: include: Step 1, obtaining the type and content of VOCs in the risk control area (17) of the contaminated site, and setting the thickness of the clean soil layer or the planting soil layer, or the thickness of the clean soil layer or the planting soil layer and the thickness of the slurry layer, so that the content of VOCs volatilized from the clean soil layer or the planting soil layer in the risk control area (17) is lower than the detection limit; Step 2, compacting the soil in the risk control area (17), and then covering the risk control area (17) with a clean soil layer or a planting soil layer according to the thickness obtained in step 1, or setting a slurry layer, a clean soil layer or a planting soil layer from bottom to top above the risk control area (17); and planting vegetation on the clean soil layer or the planting soil layer; Step 3: collecting surface VOCs content and soil moisture data of the risk control area (17) through the VOCs detection module (11) and the soil moisture detection module (13); collecting water level data of the first groundwater extraction well (1) or the second groundwater extraction well (2), and the groundwater monitoring well (14) through the water level monitor (9); Step 4: Controlling the operation of the VOCs pollution reduction unit according to the surface VOCs content and soil moisture data, as well as the water level data, of the risk control area (17); The step 4 specifically includes: The first groundwater extraction well (1) and the second groundwater extraction well (2) are started to extract groundwater, and the extraction groundwater flow rate is controlled at 10-5000 mL / min; the first microorganism culture tank (3) and the second microorganism culture tank (4) are started to inject bacterial liquid into the surface soil; When the water level elevation of the first groundwater extraction well (1) or the second groundwater extraction well (2) is lower than the water level elevation of the groundwater monitoring well (14), and the water level difference is greater than a preset water level difference value, the first groundwater extraction well (1) and the second groundwater extraction well (2) are stopped from extracting groundwater; When the total amount of VOCs detected on the surface of the risk control area (17) increases three times in a row or exceeds the preset value of the total amount of VOCs, the first microbial culture tank (3) and the second microbial culture tank (4) are stopped from injecting bacterial liquid into the surface soil, and the first groundwater extraction well (1) and the second groundwater extraction well (2) are stopped from extracting groundwater; When the soil moisture is greater than a preset moisture value, the first microorganism culture tank (3) and the second microorganism culture tank (4) are stopped from injecting bacterial solution into the surface soil, and the first groundwater extraction well (1) and the second groundwater extraction well (2) are stopped from extracting groundwater; the preset moisture value is not greater than , where ρ s is the soil particle density, unit: kg·dm -3 ρ b is the soil bulk density, unit: kg·dm -3 ρ w is the groundwater density, unit: kg·dm -3 .

Images